1. Field of the Invention
The invention relates generally to the field of computer display user interface systems. More particularly, the invention relates to user apparatus for moving a symbol, such as a cursor, on a display, and for entering xe2x80x9cpoint and clickxe2x80x9d commands.
2. Prior Art
The growing interactiveness of home entertainment systems, particularly cable television, interactive television, and Internet set-top boxes is placing greater demands on hand-operated controls.
Mice have been commonly used as user-manipulable apparatus. Using a mouse, a user directs the movement of a cursor across a display screen by corresponding manual mouse movements.
Joystick-type devices have also been used. One such joystick-type is a trackpoint device which has been mounted in-keyboard in many laptop computers. A trackpoint device includes a button-like structure resembling a pencil eraser. It is usually disposed between keys of a computer keyboard as a user interface in portable computers. The need for a mouse, and a flat working surface on which the user manipulates the mouse, is eliminated because the user is able to manipulate a trackpoint device entirely within the keyboard.
A conventional physical implementation of a trackpoint pointing device includes strain gauge sensors, and a post serving as a lever arm. By manipulating the post, the user flexes the strain gauges. Small analog signals produced by the strain gauges are interpreted by on-board software, and the cursor is moved accordingly.
The strain gauges produce a xc2xd percent full-scale signal change, and must be individually trimmed during manufacture to match their outputs. The manufacturing and trimming of the strain gauges, combined with the small analog signal they produce, contribute to the cost of the sensor and of the electronics required to make a trackpoint system. Moreover, the small full-scale magnitude of the signal change places a burden on the data acquisition system which processes the strain gauge signals into cursor movement signals.
Therefore, an important objective in the design and manufacture of trackpoint devices is the reduction of these costly factors.
These issues have been confronted in the design and manufacture of other types of user-manipulable electronic components. For instance, a conventional structure is taught in Hughes, U.S. Pat. No. 4,305,007, xe2x80x9cElectronic Two Directional Control Apparatusxe2x80x9d, issued Dec. 8, 1981. This patent describes a structure including four sensing electrodes, whose capacitances independently vary in response to the proximity of an external object.
The Hughes structure includes sensing electrodes that map out four quadrants. A controlling member at the end of a displaceable member supported from above by a ball joint, moves in relation to the sensing electrodes. These elements are contained within a three dimensional grounded shield box.
Unfortunately, the Hughes device is impractical for implementation in a keyboard or in a portable computer. Moreover, the Hughes structure requires considerable cost for parts and assembly. Also, the manufacturing process must include manual trimming of the electronic circuit to match the outputs of the four quadrants. Therefore, the Hughes apparatus does not provide the desired low cost.
Accordingly, it is an object of the invention to provide cost reductions in the manufacture of trackpoint user-manipulatable pointing devices.
To achieve this and other objects, there is provided in accordance with the invention an apparatus for sensing manipulation by a user and for producing signals related to the manipulation. The signals produced by such an apparatus may then be used as part of a user interface system. For instance, the signals might be used in a personal computer having a display screen, for causing movement of a displayed symbol, such as a cursor.
The apparatus has two mechanical components. The first component includes an articulating member such as a post surrounded by a first capacitive plate. Means are provided for causing the articulating member to articulate responsive to user manipulation thereof, and thereafter, to return to a quiescent position.
The second component includes a second capacitive plate, made up of a plurality of printed metalized members disposed about the articulating member substantially parallel to the first capacitive plate. Means are provided for detecting respective signals from a plurality of capacitors formed by said plates, the respective signals varying in value depending on articulation of the articulating member which alters the capacitance of the respective capacitors depending on the direction and magnitude of an applied force.
In accordance with the invention, the invention comprises inexpensive electrical components and simple mechanical components, to produce a low cost pointing device whose physical size and dimensions are suited for use in applications such as inkeyboard trackpoint devices.
The capacitors preferably include flat, electrically conductive members on a planar substrate, such as etched conductive regions on a printed circuit board, and the articulating member includes an electrically conductive member whose varying proximity to the conductive region, due to the manipulation by the user, produces a correspondingly varying capacitance value. The magnitude of the capacitance is determined by a data acquisition system, preferably including RC oscillators and a microcontroller. In accordance with suitable signal conditioning, the capacitance value is used to produce the cursor movement signals.
A device according to the invention may advantageously be employed as a pointing device for hand-held remote control applications, as well as for keyboards. Cost is a driving factor in the success of any device targeted to the consumer electronics market. The capacitive sensor and data acquisition system according to the invention (oscillator and microcontroller) provide advantageously low manufacturing costs.
The low-cost capacitive device according to the invention is also inherently less expensive than a mouse. Both pointing technologies require a microcontroller. In addition, a mouse requires two optical interrupters, two mechanical disks, a rotating ball, and a three dimensional structure to align these items. A preferred implementation of the capacitive sensor-based device according to the invention includes a conductive capacitive element attached to the circuit board, and an inexpensive integrated circuit (Schmitt Trigger NAND). The invention uses fewer components, and is easier to manufacture and assemble. The absence of moving parts exposed to the environment means the invention has advantageously low maintenance, and a low failure rate.